This invention concerns an apparatus to releasably attach a lamp to a reflector of a motor vehicle headlight, wherein the reflector has an opening therethrough for receiving the lamp, with a glass bulb of the lamp extending through the opening in the reflector from a rear side thereof, the lamp having a socket with a surrounding flange with radially positioned ears extending outwardly therefrom for extending between and engaging spring tongues formed on a resinous-plastic attaching ring affixed to the reflector surrounding the opening after a screwing-on motion of the lamp about its length axis, the positioning ears gliding along beveled contact surfaces of the tongues until the tongues, in an end position of the lamp, lie biased against the positioning ears and the flange of the socket is pressed against a seating surface facing an opposite direction from a mounting direction of the lamp.
In a known apparatus of European Patent 0 292 200 A2 for releasably attaching a lamp to a reflector of a motor vehicle headlight, not only is an attaching ring constructed of resinous-plastic but the reflector is as well. The plastic used for making the attaching ring, as well as the plastic for the reflector, must not only be heat resistant and rigid, but must also have sufficient elasticity that the spring tongues of the attaching ring can be formed thereon. Therefore, the resinous-plastic used for the attaching ring has been relatively more expensive than the plastic for the reflector. Since, however, the attaching ring is quite small relative to the reflector, this expensive plastic for the attaching ring increases the overall costs for the headlight only a little.
A glass bulb of the lamp encloses a lamp filament and a socket of the lamp is of resinous-plastic. An electric plug contact is on a rear side of the socket so that a free end thereof extends radially outwardly. A flange is surroundingly formed on the socket between the glass bulb and the plug contact to have three radial positioning ears extending outwardly therefrom, the flange being substantially thicker than the positioning ears. The positioning ears are spaced from a surface of the flange which faces in a mounting direction of the lamp. A surrounding groove is in the socket of the lamp between the flange and the glass bulb for receiving an o-ring seal.
An opening of the reflector for receiving the lamp is surrounded, on an interior side thereof, by a collar on whose interior surface the lamp sealingly lies after it has been mated with the o-ring seal surrounding the socket. An edge portion at the opening of the reflector has a seating surface for the flange of the socket of the lamp. After the lamp has been mounted, spring arms of the attaching ring lie on the positioning ears, under bias, and press the flange against the seating surface of the reflector. Thus, not only is a holding force for the attaching ring generated between the reflector and the reflector-mounted attaching ring, but also a high tension force for attaching the lamp. So that attaching measures of the reflector and the attaching ring can accept these additional high tension forces, they must be appropriately rigid. An attaching measure on the reflector includes a flange-like protrusion formed on the reflector surrounding its seating surface which is directed radially outwardly. So that this protrusion can withstand the additional tension forces and because it, like the reflector, is manufactured of a brittle plastic, it must have a correspondingly thick wall. Because of this, indentations can develop on an interior surface of the reflector or, if these do not develop, the reflector, in areas of its reflection surface, must have a wall as thick as the flange-like protrusion. The attaching ring grips behind the flange-like protrusion of the reflector with detent tabs which are formed on an outer surrounding edge of the attaching ring with their free ends extending in a mounting direction of the lamp. So that radially inwardly directed spring arms of the attaching ring always attach the lamp with a sufficiently large axial force, a spacing between the spring arms (that is their contact surfaces) and the seating surface of the reflector facing the spring arms, must have a correspondingly small tolerance. Maintaining such a small tolerance in the practice is quite difficult because it is a sum of a plurality of smaller tolerances. It is further disadvantageous that the attaching ring can only be affixed to a reflector which has an exact seating surface customed for a particular lamp.
It is an object of this invention to provide an apparatus for releasably attaching a lamp on a reflector of a motor vehicle headlight in a system of the type mentioned in the introductory paragraph in which, after the lamp has been mounted, axial forces developed by spring tongues of an attaching ring cannot affect a fastening coupling between the attaching ring and the reflector so that the fastening coupling, also when the spring tongues exert a great force against positioning ears, can be made with the smallest possible dimensions. It is a further object of this invention to provide such an apparatus for which a fixed seating of the lamp is also assured even if the attaching ring is universally used with many different headlights, and, even when, for example, the headlights have heat deformed reflectors in areas of lamp-receiving openings thereof. It is still a further object of this invention to provide such an apparatus for which a reflector, in an area of its lamp-receiving opening, can be uncomplicatedly formed and no additional parts are necessary in order to attach the lamp.